In a large, heavy saucepan, add oil and 3 popcorn kernels - cover pot and place over medium heat until you hear one kernel pop. Quickly remove the lid and add remaining kernels - re-cover the pot, leaving the lid slightly ajar, and cook, shaking pan frequently, until kernels stop popping, about 3 minutes. Remove from the heat and uncover. Place popcorn in a large bowl and remove any unpopped kernels.

In a large heavy pot, melt butter over medium heat. Stir in brown sugar and brown rice syrup - cook until the mixture comes to a boil, constantly stirring to dissolve the sugar. When it comes to a boil, stop stirring and cook syrup until a candy thermometer registers 295 degrees, about 8 to 10 minutes. Remove from the heat.

Using a wooden spoon, stir salt, vanilla and baking soda into the syrup, then quickly, but carefully, stir in peanuts and popcorn to coat. Immediately spread mixture onto a large baking sheet coated with nonstick spray, spreading caramel corn as thinly and evenly as possible. Set aside and allow to cool completely before breaking into bite-sized clusters.